Characteristics of patients
A total of 533 patients who were newly diagnosed as MM were included in this study. Among these 533 patients, there were 325 males (60.98%) and 208 females (39.02%). The median age of the patients was 61 years old (range, 23-87 years old). All patients received at least one novel agent, 476 patients (89.31%) contained bortezomib, 103 patients (19.32%) contained lenalidomide, 282 patients (52.91%) contained thalidomide, followed by stem cell transplants if possible. The median follow-up time was 35.79 (0.21-88.88) months. A total of 324 patients (60.8%) survived at the end of follow-up. All features of the patients are detailed in Table 1.
The effect of single CA on survival
According to the EMN criteria, we investigate the single CA aberration on impaction of prognosis at different clone sizes. The results presented that patients harbored 17p-, 13q-, 1q21+ showed shorter OS and patients harbored 17p-, 1q21+ have shorter PFS based on the EMN criteria. Then, we used Kaps to calculate the best cut-off value of OS and the results showed that the best cut-off value of OS were as follows: 17p - 20.1%, 13q - 85%, 1q21 + 39%, t (11, 14) 55.5%, t (14,16) 87%, t (4,14) 53.5%. Based on the cut-off value calculated by Kaps, we also found that patients harbored 17p-, 13q-, 1q21+, t(4;14), t(11;14), t(14;16)showed shorter OS and patients harbored 17p-, 13q-, 1q21+, t(11;14), t(14;16)have shorter PFS (Figure 1). The details were listed in the Table 2.
In order to identify which of the single CA aberration was really affecting the prognosis of patients, we further performed multivariate analysis of all CA and other possible survival-related parameters by Cox stepwise regression. Firstly, we analyzed the prognostic factors of PFS or OS according to the EMN criteria. The statistically independent predictors of PFS were 1q21+, 17p-, ISS stage, LDH, M-spike, gender, transplantation schemes. The statistically independent predictors of OS were 1q21+, 17p-, age, ISS stage, LDH, DS stage, M-spike. After that, we analyzed the prognostic factors of PFS or OS according to the cut-off value calculated by Kaps and the results showed that the statistically independent predictors of PFS were 1q21+, 17p-, t(14;16), ISS stage, LDH, isotype, transplantation schemes. The statistically independent predictors of OS were 1q21+, 17p-, t(14;16), 13q-, age, ISS stage, LDH, M-spike . The details were listed in the Table 3 and Table 4.
Prediction model and validation and calibration
In order to further verify whether the criteria calculated by Kaps can predict survival more accurately, we constructed two prognostic models according to the Cox multivariate analysis results of OS based on the two different criteria. We used nomograms to visualize the prediction model (Figure 2). Besides, we used calibration curve and Harrell's concordance index (c-index) to evaluate the performance of the prediction model. The results showed that the c-index (0.719; 95% CI, 0.683 to 0.756; corrected 0.707) for the nomogram established by Kaps method to predict OS was higher than that calculated by the EMN criteria (0.714; 95% CI, 0.678 to 0.751; corrected 0.696). The calibration curve of the two prognostic models was shown in Figure 3.
The impact of adverse CA number on prognosis
Finally, we analyzed the influence of the number of adverse CA on prognosis. According to the result of multivariate analysis which was calculated by the EMN criteria, we found that there were two adverse lesions: 17p-, 1q21+. Then, patients were divided into three groups: no abnormalities (204 patients, 38.27%), one abnormality (296 patients, 55.53%), two abnormalities (33 patients, 6.19%). The results of the univariate Cox regression analysis showed that the OS [HR, 1.984 (95% CI, 1.452-2.709) P < 0.001] and PFS [HR, 1.740 (95% CI, 1.357-2.232), P < 0.001] of one abnormality group and the OS [HR, 2.920(95% CI, 1.715-4.971), P < 0.001] and PFS [HR, 3.046(95%CI, 1.948-4.762)], P < 0.001] of two abnormalities group were shorter than that of the no abnormalities group. The survival curves were shown in Figure 4A and Figure 4B. Multivariate analysis showed that there were two independent prognostic factors associated with PFS in the three groups: one abnormality group [HR, 1.706 (95% CI, 1.313-2.217), P < 0.001], two abnormalities group [HR, 2.811(95% CI, 1.762-4.485)], P < 0.001]. There were also two independent prognostic factors associated with OS: one abnormality group [HR, 1.887 (95% CI, 1.355-2.630) P < 0.001], two abnormalities group [HR, 2.780 (95% CI, 1.566-4.934), P < 0.001].
The result of multivariate analysis showed there were four adverse lesions: 17p-, 1q21+, 13q-, t (14; 16). Then, patients were divided into four groups: no abnormalities (208 patients, 39.02%), one abnormality (228 patients, 42.78%), two abnormalities (86 patients, 16.14%), more than two abnormalities group (11 patients, 2.06%). The results of the univariate Cox regression analysis showed that the OS [HR, 1.595 (95% CI, 1.147-2.219) P=0.006] and PFS [HR,1.426 (95% CI,1.103-1.844), P=0.007] of one abnormality group, the OS [HR, 3.152(95% CI, 2.161-4.597) P<0.001] and PFS [HR, 2.385 (95% CI, 1.722-3.305), P<0.001] of two abnormalities group, the OS [HR, 12.755(95% CI, 6.426-25.318), P<0.001] and PFS [HR, 7.032 (95% CI, 3.720-13.292), P<0.001] of more than two abnormalities group were shorter than that of the no abnormalities group. The survival curves were shown in Figure 4C and Figure 4D. Besides, multivariate analysis showed that there were three independent prognostic factors associated with PFS: one abnormality group [HR, 1.347 (95% CI, 1.029-1.762), P=0.030], two abnormalities group [HR, 2.281 (95% CI, 1.627-3.199), P<0.001], more than two abnormalities group [HR, 7.766 (95% CI, 3.849-15.667), P<0.001]. There were also three independent prognostic factors associated with OS: one abnormality group [HR, 1.501 (95%CI, 1.059-2.128), P=0.023], two abnormalities group [HR, 2.773 (95% CI, 1.864-4.127), P<0.001], more than two abnormalities group [HR, 17.310 (95% CI, 7.972-37.583), P<0.001].